Method of and apparatus for feeding blanks

ABSTRACT

A methof of and apparatus for feeding the bottom blank of a stack of blanks into adjacent processing machinery wherein the leading edge of a stack is supported adjacent the processing machinery on a support table; the trailing edge of the stack is supported above the support table; subatmospheric pressure is applied to the underside of the bottom blank through perforations in the top of the table leading to a number of selectively operable subchambers beneath the perforated top to urge the bottom blank downward toward the table; and, the bottom blank is advanced into the adjacent processing machinery by a reciprocating feeder bar simultaneously exposing the next bottom blank to subatmospheric pressure which exposure begins at its trailing edge and continues to its leading edge as the blank being fed moves forward. The subchambers can be selectively closed so that selected portions of the underside of the blank can be exposed to subatmospheric pressure. Stop-feed means are provided for lifting the trailing edge of the stack above the feeder bar in the event of a malfunction; the same means can be operated intermittently to skip-feed blanks at one-half the normal rate.

United States Patent Thayer METHOD OF AND APPARATUS FOR FEEDING BLANKS [76] Inventor: William S. Thayer, c/o Kappers Company Inc., Kappers Building, Pittsburgh, Pa. 15219 [22] Filed: Dec. 22, 1971 [21] Appl. No.: 210,724

Primary ExaminerEdward A. Sroka Attorney-Boyce C. Dent et al.

[57] ABSTRACT A methof of and apparatus for feeding the bottom Aug. 28, 1973 blank of a stack of blanks into adjacent processing machinery wherein the leading edge of a stack is supported adjacent the processing machinery on a support table; the trailing edge of the stack is supported above the support table; subatmospheric pressure is applied to the underside of the bottom blank through perforations in the top of the table leading to a number of selectively operable subchambers beneath the perforated top to urge the bottom blank downward toward the table; and, the bottom blank is advanced into the adjacent processing machinery by a reciprocating feeder bar simultaneously exposing the next bottom blank to subatmospheric pressure which exposure begins at its trailing edge and continues to its leading edge as the blank being fed moves forward. The subchambers can be selectively closed so that selected portions of the underside of the blank can be exposed to subatmospheric pressure. Stop-feed means are provided for lifting the trailing edge of the stack above the feeder bar in the event of a malfunction; the same means can be operated intermittently to skip-feed blanks at one-half the normal rate.

30 Claims, 6 Drawing Figures 7 32 I26 i622 '5 us 5 H4 94 92 as 6 SE I04 H0 104 \\\\l I\\\\ I 96 E I 402 v IOI l/ l 9? 99 24 |o4 r I I" 105 r Patented Aug. 28, 1973 3,754,752

5 Sheets-Sheet 1 INVENTOR.

WILLIAM S. THAYER Patented Aug. 28, 1973 5 Sheets-Sheet :3

INVENTOR. WILLIAM S. THAYER BY flex, A -J Patented Aug. 28, 1973 3,754,752

5 Sheets-Sheet 3 ENTOR. WILLIAM s. AYER 5 Sheets-Sheet 4 FEED Patented Aug; 28, 1973 FEED m E 4 WT w m 2 LC. A. R C 5 m F OH L N 8 6 2 O2 8 w w w r.) m 6 & 05555 W 2 l 2 .1/0 $5 3m 6 v m m/ 7 2 8 m 4 4 52.5 15.. v 2 6.6.6:.. M/ 2 f LATCH K X UNLATCH K A UNLATCH INVENTOR. WILLIAM S.THAYER HO VAC 24 VDC /1. oc POWER SUPPLY 1 74 Rl N65 2 ,LLl

METHOD OF AND APPARATUS FOR FEEDING BLANKS BACKGROUND OF THE INVENTION l. Field of the Invention The invention relates generally to sheet feeding or delivering and more particularly to reciprocating bottom feeders utilizing vacuum assistance.

2. Description of the Prior Art Reciprocating bottom feeders are well known and widely used in processing corrugated paperboard blanks. Briefly, they comprise a support table for supporting the leading edge of a stack of blanks at an entrance into adjacent processing machinery; a backstop assembly to support the trailing edge of the stack above thesupport table; and a feeder bar which reciprocates beneath the stack and engages the trailing edge of the bottom blank to advance it into the adjacent processing machinery. The feeder bar includes a number of flexible plates or spring feeders spaced across the bar for engaging the trailing edge of the bottom blank.

A major disadvantage of reciprocating bottom feeders of the spring feeder type which has previously existed is that they cannot consistently feed extremely warped blanks because theflexible plates often fail to engage the trailing edge of such blanks. In addition, if the leading edge of the blank is curled upwards, the feeder bar merely jams the blank into a gate mechanism used to meter one blank at a time into the processing machinery. A minor disadvantage is that the flexible plates must flex continuously and they frequently break from fatigue. I

Several attempts have been made to improve such feeders by utilizing a vacuum system to flatten the warped blanks prior to engagement by the reciprocating feeder, none of which seems to have been completely successful.

For example, Shields U.S. Pat. No. 3,279,788 illustrates one type of vacuum system. This feeder uses a reciprocating vacuum chamber to urge the bottom blank downward against the chamber. The feeder is not completely effective in pulling the blank flat against the chamber since the vacuum is not applied to the whole area beneath the blank but only to a portion of the leading edge of the bottom blank. Even this vacuum is not continuously applied but only at the instant that the vacuum chamber is ready to advance and thereafter until it reaches the end of its forward stroke.

Furthermore, it is difficult to fmain tain {registration with the adjacent processing machinery which registration is usually essential in the operation of the machinery. The reason for this is that the blanks are seldom exactly the same length so that a clearance is required be tween the gate mechanism and the backstop assembly. Therefore, the blanks rest on the support table longitudinally somewhere between these parts; that is, the

leading edge of one blank may rest against the gate assembly and the trailing edge of the next blank may rest against the backstop assembly. The reciprocating vacuum chamber engages the bottom blank wherever it may be resting between the gate and backstop. Thus, registration may vary by the amount of the clearance dimension. Shields attempted to overcome the problem of registration by using a conventional reciprocating feeder bar in addition to the reciprocating vacuum chamber. However, it appears that this still does not correct the register problem because, if the blank does not slip against the vacuum chamber, it will actually be advanced by the vacuum chamber; the feeder bar never has a chance to engage the trailing edge of the blank. Thus, registration may still vary by the amount of the clearance dimension. In addition, intermittently applied vacuum requires the use of seals, porting, and the like which adds to the cost and maintenance of the system.

Another example is shown in Ward et al. U.S. Pat. No. 3,588,095. In the Ward feeder, a stationary vacuum chamber is used rather than a reciprocating vacuum chamber. The vacuum chamber covers most of the whole area beneath the stack and draws the bottom blank completely flat against the vacuum chamber where it is then advanced by a thin reciprocating feeder bar lying flat against the chamber behind the blank. The bar includes a thin ledge or lip for engaging the trailing edge of the blank.

The longitudinal dimension of the bar along the path of advance is greater than its stroke length during reciprocation. Thus, the feeder bar blocks the vacuum to the underside of the next blank until the bar separates from thetrailing edge of the blank being fed as the bar begins its return stroke; this arrangement is said to result in vacuum being applied first to the approximate centermost portion of the next blank to be fed. Thus, vacuum is not applied to the trailing edge of the blank until the instant before the feeder bar is in position to begin its advance stroke.

Satisfactory operation of the Ward et al feeder depends on the trailing edge of the warped blanks being urged perfectly flat againstthe vacuum chamber to enable the thin feeder bar to engage the bottom blank. When the blanks are extremely warped, the amount of vacuum required to flatten them may be excessive and it may be difficult for the feeder bar to overcome the frictional engagement between the blank and chamber without damaging the trailing edge of the blank. It is also necessary to mask off the area of the vacuum chamber outside the area of small blanks to prevent loss of vacuum. A second vacuum chamber located behind the primary chamber can be shut off if the blanks do not extend behind the primary chamber.

Accordingly, an object of the. present invention is to providean improved method of and apparatus for feeding the bottom blank of a stack of blanks into adjacent processing machinery which utilizes the advantages of advancing the bottom blank by engaging its trailing edge above a support table that supports its leading edge while applying subatmospheric pressure to substantially the complete underside of the blank to urge it toward the support table and against the support for its trailing edge and simultaneously exposing the next blank to subatmospheric pressure beginning with the advance of the bottom blank. I

SUMMARY OF THE INVENTION The improvements provided by this invention are accomplished by supporting the leading edge of the bottom blank of the stack at a first height for entry into adjacent processing machinery by a first support means while supporting the trailing edge of the bottom blank of the stack at a second height above the first support means by a second support means, applying subatmospheric pressure to the underside of the bottom blank by a vacuum means to urge it downwardly against both the first support means and the second support means,

and advancing the bottom blank into the adjacent processing machinery by a reciprocating feeding means engageable with the trailing edge of the bottom blank at the second height while continuing to apply subatmospheric pressure by the vacuum means first to the trailing edge of the next bottom blank and continuing therefrom toward its leading edge during advancement of the bottom blank.

The first support means comprises a support tablewith a perforated top beneath which is located a number of vacuum chambers which can be selectively supplied with subatmospheric pressure by manually operable valve means to limit the application of subatmospheric pressure to only the underside of the bottom blank.

The trailing edge of the stack is supported above the support table by a backstop assembly which is longitudinally adjustable toward the adjacent processing machinery to pennit feeding of selected blank sizes. The backstop assembly may include stop-feed means for raising the trailing edge of the stack upon command to prevent engagement of the advancing feeding means with the trailing edge of the bottom blank in the event of a malfunction of the equipment. The stop-feed means may also be cyclically operated to prevent feeding engagement of the advancing means with the bottom blank during alternate reciprocations thereof to provide skip-feed operation of the feeder. 7

Although conventional spring-feeder plates may beused on the feeder bar for advancing the bottom blank, rigid plates are preferably used since they are not subject to bending fatigue and since, with this improved feeder, the trailing edge of thebottom blank is urged firmly into engagement with the edge engaging ledge or lip on the rigid feeder.

Preferably, the perforated plate includes a pair of runners flush with the top of the plate and spaced across the width of the machine to support the feeder bar slightly above the plate during feed strokes of the bar. Small pads of polytetrafluoroethylene (PTFE) secured to the bar over the runners reduce friction between the feeder bar and runners.

The subatmospheric pressure or vacuum is supplied to the vacuum chambers under both dynamic and static conditions. At the beginning of the feed cycle when the feeder bar is at its rearmost position, the front of the bottom blank rests on the feed table and the back of the blank is supported above the table by the backstop assembly. Thus, there is an air space beneath the bottom of the blank and the top of the support table. As negative pressure is created in the vacuum chambers, air will flow from the air space, through the perforated top, into the chambers, and through the supply system. It is this air flow that urges the bottom blank towards the support table and backstop assembly. Since the air flow is dynamic in character, it can be controlled by the valve means in the vacuum chambers to establish a dynamic pressure profile as will be subsequently explained.

Once the blank, or a portion thereof, rests against the perforated top, air flow through the perforations covered by the blank ceases. Thereafter, static pressure maintains the blank against the top of the perforated plate. The magnitude of the static pressure is controlled by a damper means which preferably regulates the volume of air removed from the chambers. This creates a static pressure profile which is substantially equal in magnitude beneath the portion of the blank resting on the perforated top as will be subsequently explained.

The valve means used to control the air flow into the vacuum chambers preferably comprise flat plates slidable over a vacuum supply'opening to the chambers. By positioning the plates to be partly or fully open, the air flow through the chambers can be varied as desired. For example, it may be desirable to apply less air flow to the front chambers beneath the leading edge of the bottom blank than to the rear trailing edge. In this event, the valves in the front chambers can be partially closed to reduce the air flow'. The valves may be selectively positioned to provide any desired air flow profile.

The damper means used to control the negative static pressure in the vacuum chambers preferably comprises a manually operable damper, such as a butterfly valve or slide gate, in a discharge outlet of the vacuum pump used to supply the negative pressure. With the damper fully open, the vacuum pump discharges a maximum amount of air flowing through the system. Partially closing the damper restricts the discharge outlet thereby creating a back pressure in the system which reduces the static, pressure therein.

If desired, a manually operable vent to atmosphere may be included in a supply duct connecting the vacuum pump to the vacuum chambers instead of a discharge damper. By selectively opening the vent, part of the air discharged by the pump will be drawn from atmosphere and part from the vacuum chambers thereby reducing static pressure in the chambers. The damper is preferred since horsepower requirements for the pump are more dependent on the volume of air discharged rather than static pressure.

Two vacuum pumps are preferably used with both being connected through a common duct to all the vacuum chambers. Thus, by using only one pump, the magnitude of the air flow can be reduced; the dynamic air flow profile is provided by the setting of the valves and operates independently of the number of vacuum pumps used.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings wherein like parts are marked alike:

FIG. 1 is a perspective view of the feeding machine with portions removed to illustrate the subchambers and associated valve means beneath the perforated top of the first support means and one of the vacuum means beneath the first support;

FIG. 2 is a diagrammatic side elevation in crosssection of the feeding machine of FIG. 1 illustrating the advance of the bottom blank from beneath a stack of blanks thereon and the location and direction of air flow creating dynamic and static subatmospheric pressure beneath both the bottom and next bottom blanks;

FIG. 3 is a perspective view of a portion of the reciprocating feeder bar utilizing a rigid feed plate with a cutaway portion illustrating the slide members for supporting the feed bar slightly above the first support means;

FIG. 4 is a diagrammatic side elevation in crosssection of the backstop assembly illustrating the arrangement for providing stop-feed and skip-feed functions;

FIG. 5 is a schematic illustrating the electrical and air connections for the backstop assembly of FIG. 4; and

FIG. 6 is a schematic illustration showing the velocity of the feeder bar at various positions along its stroke.

DESCRIPTION OF THE PREFERRED EMBODIMENT The improved blank feeding machine is generally denoted by numeral 10 as illustrated in FIGS. 1 and 2. The feeding machine 10 generally includes a first support means 12 for supporting the leading edge-l4 of the. bottom blank 15 of a stack of blanks 16 at the proper height for entry through a metering means 18 into adjacent processing machinery (not shown) which performs further operations on the blanks; a second support means 20 secured on top of the first support means 12 for supporting the trailing edge 22 of the bottom blank 15 of the stack of blanks 16 above the first support 12; vacuum means 24 for applying subatmospheric pressure to substantially all of the underside of the bottom blank 15 of the stack to draw the bottom blank 15 downward against the top of the first support means 12 and against the second support means 20 which supports the trailing edge portion 22 above the first supgaging the trailing edge 22 of the bottom blank 15 and advancing it into the adjacent processing machinery. As the bottom blank 15 is advanced, the subatmospheric pressure being applied through the first support means 12 is first applied to the bottom of the next bottom blank at its trailing edge 32 as it becomes exposed by advance of the bottom blank 15 and continues to be simultaneously applied toward its leading edge 34 as the bottom blank 15 is advanced.

More specifically, the first support means or bed 12 is supported by machine side frames 36L and 36R. The top of the bed defines a metered opening 38 with the bottom of a front guide assembly 40 which is a part of the metering means 18 and is arranged to permit only a single blank to pass through the metered opening 38 at any one time. As the blank 15 passes through the opening, it is engaged by a pair of pull rolls 42U and 42L which continues to advance the blank into the adjacent machinery.

The front guide assembly 40 includes a pair of support bars 44U and 44L secured between the machine side frames 36L, 36R. A pair of front guides or gates 46 are supported on the support bars 44U, 44L in the conventional manner. The gates 46 include a suitable clamp and screw arrangement (not shown) for positioning the front faces 48 of the gates 46 at a distance above the bed 12 corresponding to the thickness of the blank passing through the metered opening 38. The gates 46 are slidable across the support bars 44U, 44L so that they can be positioned at a distance corresponding to the width of the blanks being processed.

A pair of side guides 50 are also supported on the support bars 44U, 44L outboard of the gates 46. The side guides 50 are also slidable across the support bars and can be similarly clamped in position. The side guides 50 include front faces 52 and side faces 54 which are normally spaced apart at a distance slightly greater than the width of the sheet to maintain the stack of blanks 16 in vertical alignment.

The pair of pull rolls 42 are rotatably mounted between the machine frames 36 immediately behind the front guide assembly 40. These rolls are spaced to engage the thickness of a single blank advanced between them by the advancing means 26 on the bed 12 and grip the blank firmly so as to continue advancing the blank into the adjacent machinery.

The bed 12 is provided with a perforated top 56 in an area between a pair of guide slots SSL and 58R in the bed 12 for the reciprocating feeder 26; the top 56 extends from the leading edge 60 of the bed 12 to the trailing edge 62 except for an operator access area 64 as best shown in FIG. 1. Negative pressure of vacuum is applied beneath and through the perforated top 56 to draw the bottom blank 15 down against the top which will be later explained in greater detail.

The second support means 20 comprises a backstop assembly including a backstop support bar 66, preferably in the form of a channel as best illustrated in FIG. 4. The bar 66 is pivotally supported on a pivot rod 68 by a pair of support blocks 70 secured to the bar. The rod 68 is supported by a pair of clamp blocks 72 slidably engaged in guide slots 74 in the bed 12. This permits the backstop assembly 20 to be adjusted toward and away from the front guide assembly 40 at the leading edge '60 of the bed 12. The guide slot arrangement is conventional and comprises grooves 74 formed in the bed 12 with guide plates 76 secured along the edges thereof to form a T-slot as best shown in FIG. 1. A screw 78 passing through the clamp block 72 and into a clamp nut 80 beneath the guide plates 76 secures the backstop assembly 20 in position at the desired location corresponding to the length of the blanks being fed. A handle 82 secured to the screw 78 aids in clamping the assembly. The backstop assembly 20 also includes a number of backstops 84 secured to the support bar 66. A screw 86 in the bottom of each backstop 84 secures a support ledge 88 thereon and acts as a stop to maintain the backstop see FIG. 4) parallel with the top of the bed. The air cylinder 90 illustrated in FIG. 4 will be described later in connection with the stopfeed and skip-feed arrangements.

The vacuum means 24 for applying subatmospheric pressure'or vacuum through the perforated top 56 of the bed 12 includes a number of subchambers 92 formed in the body of the bed 12 beneath the perforated top 56 by a number of vertical walls 94 which in effect sectionalize the bed beneath the perforated top. Beneath the subchambers 92 is a supply duct 96 in communication with all the subchambers. The supply duct 96 may be formed integrally with the body of the bed or made from sheet metal and connected thereto.

A conventional motor-driven vacuum pump 98 is mounted beneath the supply duct 96 with an inlet 100 connected to the duct as illustrated in FIG. 2. A crosstie 102 extends between the side frames 36 and beneath the bed 12 to support it along with the side frames. A bracket 105 secured to the crosstie 102 supports the vacuum pump 98 beneath the supply duct 96. Preferably, a pair of vacuum pumps 98 is used as illustrated in FIG. 1. Both pumps 98 are connected to the supply duct 96 which lies beneath all of the subchambers 92. In this fashion, the air flow can be doubled by using both vacuum pumps 98 simultaneously.

As indicated by the arrows 104 in FIG. 2, air is evacuated by the vacuum pumps 98 from beneath the stack 16. The air passes first through the perforations 106 in the perforated top 56 and into the subchambers 92; from there into the supply duct 96, and then through the vacuum pumps 98 to atmosphere.

As best seen in FIG. 2, an air space 17 is defined behind the bottom blank 15, the bottom of the next blank 30, and the top of perforated plate 56. As blank 15 advances, the air space becomes longer because the trailing edge of blank 15 exposes more'of blank 30 to negative pressure as it advances. Air from space 17 is drawn through perforations 106 into the subchambers 92 beneath space 17. This creates a dynamic air flow which draws the trailing edge 32 of blank 30 downward against the support ledges 88 of backstops 84.

On the other hand, the portion of blank 15 resting on perforated top 56 closes perforations 106 beneath that portion. Since no air can flow through the closed perforations, this portion of the blank is subjected to static negative pressure which will be substantially equal in all of the subchambers beneath the portion of the blank resting against the perforated top.

Each subchamber 92 includes a valve 108 comprising an opening 110 between the subchamber 92 and the supply duct 96 and a valve plate 112 which is slidable over the opening 110. When the plate 112 covers the entire opening, no air is evacuated from that particular subchamber; with the plate fully open, the full strength of the vacuum pump 98 is applied to the subchamber to evacuate the maximum amount of air and create maximum air flow. With the plate only partially open, the air flow is reduced an amount corresponding to the amount that the valve plate is opened although the relationship is 'not necessarily linear.

In this manner, the magnitude of. airflow in each sub* chamber 92 can be regulated to provide the desired air flow profile for drawing the bottom blank against top 56. For example, the plates 1 12 may be regulated in the front row of subchambers 92 along the leading edge 60 of the bed 12 to provide only one-half the maximum possible air flow through them whereas the remainder of the valves 112 may be fully open to provide the full air flow to the underside of the remaining portion of the bottom blank 15 that is supported above the top 56. The valves 108 for the subchambers 92 falling outside the area of the blank being fed may be closed so that vacuum is applied only to the underside of the blank itself. Thus, no'masking off of the areas outside the blank is necessary. By selectively opening and closing the valves 108, or by partial opening thereof, any desired air flow profile beneath the blank can be obtained to suit the particular warped condition of the blanks.

The valve plate 112 is connected to an upstanding post 114 (only one shown in FIG. 1) rotatably mounted in the bottom of the subchamber 92. The post 114 extends through a hole 116 in the perforated plate 56 so that its top end is flush with the top of the plate. The post 114 preferably includes a necked-down flat portion 118 on its top so that it can be grasped to turn the valve plate 112 to the position desired.

As previously explained, the subchambers 92 beneath the perforations 106 closed by a portion of a blank lying thereonare subject to static negative pressure. Without an air flow through the subchambers 92, the valves 108 obviously have no effect on the vacuum applied to portions of the blank covering the subchambers except when they are fully closed. Thus, the static vacuum pressure is substantially equalized between such subchambers.

Sometimes, because of the thickness of the blank or its overall size or other characteristics the maximum amount of static negative pressure which can be applied by the vacuum pumps 98 to the bottom of the blank causes it to adhere too tightly to top 56. This may result in the blank being buckled by the advancing feeder bar, causing a jam-up in the feeder. Thus, it is desirable to be able to regulate the amount or magnitude of static negative pressure to reduce the holding force between the blank and top 56.

The static pressure can be easily reduced by turning off one of the vacuum pumps 98. However, if only a single pump system is used, or if some level of pressure is desired that falls between the levels supplied by one or two pumps, then further regulation is desirable.

The preferred means for providing such regulation comprises a damper means 97 positioned across the discharge end of the exhaust duct 99 of pumps 98. Damper means 97 may include a conventional slide gate 101 mounted for sliding movement between a pair of slides secured to bracket 105 (the slide connection has been omitted from FIGS. 1 and 2 for clarity). Gate 101 includes an opening defined by louvres 103 (or a wire screen or the like) which, when positioned in front of duct 99 permits unrestricted discharge of air from pump 98.'By sliding gate 101 to a position where louvres 103 are out of alignment with duct 99, the discharge of air from pump 98 is prevented. Thus, by selectively positioning the gate 101 between a fully open and fully closed position, the volume of air evacuated by pumps 98 from subchambers 92 can be regulated as desired. This, of course, affects the static pressure in the vacuum system, that is, the negative static pressure can be reduced as desired. Suitable clamps (not shown) are provided to lock gates 101 in the position selected.

Should it be desirable to maintain full volume rather than restricted air flow, a vent means 107 may be used instead of damper means 97. The vent means 107 is also shown in FIG. 2 although both a vent means and damper means would not ordinarily be used.

Vent means 107 may comprise a slide gate 109 mounted for sliding movement over an opening 109A in supply duct 96. By selectively positioning slide gate 109 between a fully open and fully closed position, the supply duct can be vented to atmosphere. Thus, part of the air evacuated from the system by pumps'98 will come directly from atmosphere and'the remainder will come from subchambers 92. This, of course, reduces the static pressure in subchambers 92. The vent means 107 is located in the supply duct 96 between the pumps 98 and subchambers 92 so that the total volume of air discharged by pumps 98 remains constant. Although vent means 107 is shown in FIG. 2 as being located beneath duct 96, a better location (not shown) would be in the front face of duct 96 in the operator access area 64 shown in FIG. 1. Thus, venting would have a more equalized effect on the complete system.

As previously mentioned, bed 12 includes an operator access area 64 to permit an operator to stand close to the trailing edge of the stack when short blanks are being fed. When long blanks are fed, the trailing edge of the stack is supported by the backstop assembly 20 across the access area 64. However, no vacuum is applied to the underside of the bottom blank in the area 24. Since the blanks may be warped in this central area, it is also desirable to provide vacuum to draw the trailing edge downward toward the backstops 84 across the width of the access area 64. This can be done by mounting an access area support 1 11 or bed leaf across the area 64.

Access support 111, as shown in FIG. 1, includes a perforated top 113 similar to top 56 and is hollow beneath the top 113 in a manner similar to subchambers 92. Vacuum is supplied to the support 111 by a flexible hose 115 connected to the support 111 and to the main supply duct 96. A slide gate (not shown) similar to slide gate 101 may be positioned across the entrance to hose 115 at the supply duct 96 to either provide or prevent vacuum supply to support 111. If desired, a valve (not shown) similar to valves 108 may be used at the entrance of hose 115 into support 111 to control air flow through perforated top 113.

Support 111 is supported by a conventional springloaded slide pin assembly 117 whose pins protrude into grooves 119 on the sides of bed 12 around access area 64. Grooves 119 may be formed integrally in bed 12 or formed by a strip 121 spaced beneath runners 132. Another similar spring pin assembly 123 secured to the top of backstop barchannel 66 may be used to connect the bar assembly 20 to support 111'. Thus, as backstop assembly 20 is positioned along bed 12 toward gates 46, support 111 will automatically be positioned also.

When the position of support 1 1 1 causes interference between its forward edge and bed 12, the support 111 is first disconnected from backstop assembly thereafter the pins of assemblies 117 on the rear edge of support 111 are retracted. This permits support 111 to pivot downward about the forward pin assemblies 117 (not shown) to a vertical position. Then the backstop assembly can be moved to the desired position along bed 12 and opens up access area 64 for use by the operator. Hose 115 flexes into a somewhat coiled position behind support 111.

The feeder bar assembly 26 comprises a feeder bar 120 clamped to a pair of slides 122 each of which reciprocates in a corresponding T-slot groove 58L and 58R formed in the bed 12 as best illustrated in FIG. 1. Slides 122 each include a T-slot groove 123; clamp bolts (not shown) pass through bar 120 and are threaded into T- slot nuts (not shown) in groove 123 in the conventional manner to clamp bar 12 to slides 122. A number of feed elements or clips 124 are spaced at intervals along the feeder bar 120. Each clip 124 includes a blank gripping edge 126 for engaging the trailing edge 22 of the bottom blank 15. Bar 120 is clamped to slides 122 so that edges 126 are spaced from the front gate surfaces 48 at a distance slightly greater than the length of the blank being fed when the slides are in their furtherest rearmost position. A drive means (not shown) is connectedto the slides 122 to make them reciprocate along the grooves 58 thereby carrying the feeder bar 120 with them. The drive means is usually arranged to produce a sine wave velocity curve so that the feeder assembly 26 engages the trailing edge 22 of the bottom blank 15 at near zero velocity and accelerates it to maximum velocity. The geometry is arranged so that the leading edge 34 of the blank 15 is engaged by the pull rolls 42 when the feeder reaches maximum velocity at about the midpoint of its forward stroke. The blank 15 leaves the feeder assembly 26 as the feeder slows down on the deceleration portion of the velocity curve. After stopping, the feeder returnsto the beginning of its feed stroke.

As the bottom blank 15 is advanced by the feeder assembly 26, the trailing edge 32 of the next bottom blank 30 is exposed behind the advancing blank 15, beginning at the edge of trailing surface 32. Since the vacuum is continuously applied, the air flow through the open perforations begins urging the trailing surface 32 of the next bottom blank 30 downward toward the bed 12 as soon as it becomes exposed by the advance of the bottom blank 15. Thus, the vacuum force on the next bottom blank 30 follows the trailing surface 22 of the bottom blank 15 simultaneously during advancement thereof. As the bottom blank 15 clears the front guide assembly 40, the next bottom blank 30 is completely exposed to the air flow and is urged firmly against the perforated top 56, except for the trailing edge surface 32 supported by backstops 84; by this time the feeder assembly 26 has returned to its initial feeding position.

The foregoing is schematically illustrated in FIG. 6 in which panel 6v shows the instantaneous velocity of the advancing means 26 at sequential positions throughout the feed cycle. In accord with conventional practice, a crank gear (not shown) rotating at constant velocity imparts a reciprocating motion to advancing means 26. The velocity of the crank gear is shown beginning at point 0 on the right of the zero velocity line and ending at point 0 on the left along the path with the arrows. The crank gear is connected to the advancing means 26 in a manner to impart maximum velocity to the advancin'g means at point 3 during the feed stroke and a lesser maximum velocity at point 6 on the return stroke, the latter being shown by the dotted line with the arrow. Thus, the advancing means begins at zero velocity at point 0, advances to maximum feed velocity at point 3, reaches zero velocity at point 5, advances to maximum return velocity at point 6, and reaches zero velocity at beginning point 0.

At-the beginning of the feed stroke, a gripping edge 126 (see FIG. 3) on advancing means 26is usually set by the operator at about one-fourth to one-half inch behind the trailingedge 32 of the bottom blank resting on perforated top 56 as shown by the dotted line extending perpendicular to beginning point 0. As the edge 126 advances, it grips the edge 32 of the blank at point 1. This is shown by another perpendicular dotted line from point 1. The edge 26 continues to accelerate to point 3. At this point, the leading edge of the blank has advanced through the' metered opening 48 (FIG. 2) and into the nip formed by feed rolls 42U and 42L. The feed rolls are rotatingat the same velocity as point 3 on the feeder velocity curve as shown by the horizontal line extending to the left of point 3. As the blank enters the feed roll nip, it is engaged by the feed rolls which then continue to advance it at uniform maximum velocity.

From point 3, the edge 126 decelerates until it reaches zero velocity at point 5. Thus, it can be seen that the trailing edge 32 of the sheet will begin to separate from edge 126 at point 3. Panel 6d shows this by the dotted perpendicular line from point 3. Thus, by the time edge 126 has decelerated to point 4, the trailing edge 32 has advanced at uniform maximum velocity to point 4' along the feed roll curve. This causes a separation between the trailing edge 32 and gripping edge 126 as shown in panel 6e. The separation continues to grow and will be approximately as shown in panel 6f when the edge 126 has stopped at point at the furtherest end of the feed stroke. At this point, edge 126 begins its return stroke while the sheet continues to advance. By the time the edge 126 reaches maximum return velocity at point 6, edge 32 will be at point 6' as shown in panel 63. Perpendicular lines from the various points identify the position of the trailing edge 32 and gripping edge 126.

Meanwhile, suction is continuously applied to the underside of the blanks through perforated top 56 throughout the feed cycle. Suction is applied to only the bottom blank when it is in the position shown in panels 6a and 6b as denoted by arrows A. However, as the bottom blank advances, it exposes the trailing portion of the next-to-be bottom blank as shown in panel 6c. Thus, suction is first applied to the trailing portion of the next bottom blank as indicated by arrow B in panel 6c. As the bottom blank continues to advance, more of the next bottom blank is exposed to suction as indicated by arrows B in the succeeding panels until the suction is applied only to the next bottom blank as the first blank passes beyond the face 48 of the front guide. Thus, it can be seen that suction applied first to the trailing portion of the next bottom blank simultaneously follows the trailing edge 32 of the bottom blank during advancement thereof. It can also be seen that the complete blank will be drawn against the perforated top 56 except the trailing portion supported above the top 56 by ledges 88 (FIG. 4). The only interference between the suction and the blank is that presented by the area of the feeder bar 26 itself in the position shown in panel 6b. However, its width in the direction of travel is comparatively small so that suction is almost immediately applied to the trailing portion of the next bottom blank as the bottom blank is advanced as shown in panel 60. During the remainder of the feed and return strokes, the interference presented by the feeder bar moves along the feed and return paths so that it has no detrimental effect on the application of suction. For example, the width of the feeder bar may be as narrow as 3% inches on a machine where the length of the bed'in the direction of blank travel is 75 inches or more and the length of the feed stroke is approximately 10 inches. Thus, the width of the feeder bar constitutes only a minor fraction of the area of the feed surface.

The feeder bar shown in FIG. 1 includes a number of conventional flexible feed clips 124 mounted to the feeder bar 120. These feed clips 124 are adapted to flex upward above the bar 120 an amount necessary to enable the gripping edge'l26 to engage the trailing edge of a warped blank. As the feeder assembly 26 advances, the clips are compressed by the weight of the stack. Because of this continuous flexing, the feed clips 124 are subject to failurefrom fatigue. However, in the present feeding machine 10, the bottom blank is urged downward towards the bed by vacuum so that the trailing edge of the blank is substantially straight. It has been found that a rigid feeding clip 130 as illustrated in FIG.

3 may be'successfully used. Its foremost advantage is that it will not fail from fatigue. Second, it is safer to use because there is no space between it and the feeder bar in which an operators fingers can be caught.

Although the serrated edge 126 shown on the rigid feeder clip 130 in FIG. 3 is preferred because it effectively grips the trailing edge of the blank, a straight knife edge (not shown) without serrations will also feed blanks satisfactorily.

Another advantage of applying the vacuum to the trailing surface 32 of the second blank immediately as the first blank 15 begins to advance is that the second blank is substantially continuously urged downward against the top of the feeder clips 124 or 130 throughout the feed and return stroke of the feeder assembly 26. Thus, by the time the feeder 26 returns to its initial feed position, the trailing edge of the blank will only need to move downward a distance equal to the thickness of the gripping edge 126 to be in position for feeding. Therefore, there is little possibility that the gripping edge 126 will fail to engage the trailing edge of the blank.

Since the feeder bar 120 is usually made of aluminum because of its favorable strength to weight ratio, and since the perforated top 56 of the bed 12 is preferably made of steel, it is desirable to provide a pair of wear strips 132 flush with the top surface of the perforated plate 56, in the position shown in FIG. 1, upon which the feeder bar 120 can slide during reciprocation. The strips 132 can be made of material compatible with aluminum such as brass, for example. However, a better arrangement is to use small plugs 134 of PTFE inserted in the feeder bar 120 as shown in FIG. 3. The plugs 134 include shoulder portions 136 that rest against the wear strips 132 and the bottom of the feeder bar 120 and, because they are made of PTFE, provide continuous dry lubrication between them and the wear strips. The inserts need not be plugs as shown but may be a strip of solid material (not shown) suitably secured to the underside of the feeder bar.

The stop-feed arrangement previously referred to is best illustrated in the diagrammatic view of FIG. 4. A conventional air-operated cylinder or ram 90 has a body trunnion 140 mounted to a pair of side brackets 142 by pins 144 in the usual manner; the brackets 142 are secured to the top of the backstop bar 66. The rod end 146 of the cylinder 90 is attached to an upstanding portion'l48 of the clamp block 72, which secures the backstop assembly 20 to the bed 12, by an ordinary pin and clevis connection 150.

When air is applied to one side of the piston (not shown) inside the cylinder 90, the backstop bar 66 pivots around the pivot shaft 68 thereby carrying all the backstops 84 to the feed position shown with the screw 86 butting against the bed acting as a stop. When air is applied to the opposite side of the piston 90, the backstop bar 66 pivots in the opposite direction around the pivot rod 68 thereby carrying all the backstops with it to the position partially shown by the dotted lines 152. This, of course, lifts the edges 88 with the trailing edge 22 of the blank 15 resting thereon upward above the bed 12. The travel is sufficient to lift the trailing edge 22 of the bottom blank 15 above the gripping edge 126 of the feed clips 124 or 130 on the feeder bar 120 so that as the feeder 26 advances from its initial starting position, the gripping edges 126 do not engage the bottom blank 15. Thus, in the event of a malfunction or jam-up, the operator can energize the air cylinder 90, as will be subsequently explained, to raise the trailing edge of the stack and prevent any further feeding of blanks until the malfunction is corrected. In this man ner, jam-up of blanks in the machine is avoided.

The air cylinder 90 can also be operated cyclically to lift the stack 16 out of engagement with the feed clips 124 or 130 on alternate advance strokes of the feeder bar 66. Thus, blanks will be advanced only on every other forward stroke of the feeder bar to achieve skipfeed operation. A full explanation of skip-feed 'functions is pointed out in Schulz US. Pat. No. 3,038,720.

The manner of energizing the air cylinder 90 to achieve stop-feed or skip-feed operation is illustrated in the schematic of FIG. 5. The circuit generally denoted by numeral 198 includes a push-pull feed switch 200 for controlling the stop-feed function and a selector switch 202 for controlling the skip-feed function. These switches are connected in series between power leads L1 and L2 supplied with 110V AC current. Also in series with the switches is a coil C1 of a conventional electrically controlled pneumatic solenoid valve 204. This valve is arranged to supply pneumatic pressure to the air cylinder 90 which controls the position of the backstops 84. When coil Cl is energized, pressure is supplied to cylinder 90 to extend piston rod 146 thereby pivoting the backstops 84 to their lower or blank feeding position. Thus, with selector switch 202 in the regular feed position and push-pull switch 200 pulled to the start position, coil C1 will be energized by current flowing in lead 206 through the contacts 208 and 210 of switches 200 and 202. In this state of operation, the remainder of the circuit is de-energized, there being no completed connections to it.

In the event of a malfunction or other reason for stopping the machine, switch 200 is pushed. This opens contacts 208 and closes contacts 212 of switch 200. The input side of contacts 208 and 212 are jumpered by lead 214; thus, current will flow through contacts 212 through lead 216 to energize a second coil C2 in valve 204 via lead 218 and on to L2. When coil C1 is energized, the valve 204 supplies pneumaticpressure to cylinder 90 to retract piston rod 146 thereby pivoting backstops 84 to the raise or non-feeding position.

Lead 218 is connected to lead '220 which supplies current to the input side of a conventional DC. power supply 219 which provides 24 V DC toanother portion of the circuit. Normally closed contacts R2 permit curward stroke and in the lowered position during the next I forward stroke.

rent in lead 218 to flow to lead 220. However, lead 220 includes another set of contacts 224 in switch 200. When switch 200 is pushed to stop as described above, contacts 224 are opened. Thus, current cannot flow to the remainderof the circuit from lead 220 and therefore it-remains de-energized.

The foregoing has described the arrangement and operation of the stop-feed functions. If desired, switch 200 may be operated automatically by malfunction detectors (not shown). The arrangement and operation of the skip-feed function is as follows. I

A set of contacts 226 in switch 202 are connected'to LI by jumper 228 between contacts2l0 and 226 and to lead 206 by lead 230 and to lead 218 by lead 232. Lead 230 includes a set of normally open contacts R2. Thus, with contacts 208 of switch 200 closed, when selector switch 202 is moved toclose contacts 226, current flows in leads 230, 232, and 218. Current cannot flow to coil Cl because normally open contacts R2 are open but will flow ,to coil C2 through normally closed contacts R2 thereby energizing coil C2 to raise backstops 84 to a non-feeding position. Current will also flow in lead 220 to DC. power supply 219 through contacts 224 which'are now closed by switch 200 thereby energizing the remainder of the circuit for skip-feed operation.

To do this, contacts R2 are alternately opened and closed. Thus, when N.C. contacts R2 are closed, coil C2 is energized as previously described; when No.

contacts R2 are closed, current flows from contacts 226 to lead 206 through lead 230 and NO. contacts R2 thereby energizing coil Cl and lowering the backstops 84. At the same time, current will flow through leads 232 and 220, through closed contacts 224 to DC. power supply 219 thereby maintaining the remainder of the circuit energized.

Generally, the skip-feed portion of the circuit operates as follows. Contacts R2 are alternately opened and closed by a vane operated magnetic switch 236. A vane 238 is attached to the end of a shaft 240 which is arranged to make one complete revolution for each feed cycle (forward and return) of the feeder bar 120 as shown by arrow 241 in FIG. 1. The vane passes through a slot 242 in switch 236 during each revolution of shaft 240; this arrangement is conventional and well known by those skilled in the art.

As the vane 238 passes through the slot 242 contacts 244 of switch 236 are closed and then opened automatically. Now, assuming thatvane 238 is just entering slot 242, contacts 244 will close; this pulls in a maintained contact type relay R1 connected in series with switch 236 by lead 238 between DC. power leads LLl and LL2. Relay R1 includes normally open contacts R1 and normally closed contacts R1; contacts R1 supply current to a flipfiop relay circuit 250 shown within the dotted lines on FIG. 5. Flip-flop circuit 250 operates so as to energize another maintained contact type relay R2 on every other advance stroke of feeder bar 120; thus, the contacts R2 of relay R2 are alternately opened and closed to alternately energize coils CI and C2 to raise the backstops 84 on alternate feed strokes thereby providing skip-feed operation.

Specifically, the skip-feed portion of the circuit 198 is arranged and operates as follows. The DC. operated portion of the circuit below power supply 219 includes switch 236 and relay R1 as previouslyvdescribed. It also includes flip-flop circuit 250, shown within the dotted lines on FIG. 5, which comprises a pair of identical relays N and F generally connected in parallel between DC. power leads LLl and LL2. Relays N and F are conventional latching relays having contacts which change state by momentary energization of their respective coils provided that the contacts are not already in the position caused by such energization.

The flip-flop circuit 250 controls the open and closed positions of contacts F1 and F2 of relay F. A corresponding contact F2G, connected in series with relay R2 by lead 260 between VAC power leads L1 and L2, is ganged to relay F contact F2 and, therefore, follows its operation. Flip-flop circuit 250 is arranged, as will be subsequently described, to close contact F2G on alternate forward strokes of feeder bar 120. Closing of contact F2G energizes relay R2 thereby changing the state of its contacts R2 connected to coils Cl and C2 during such energization. Thus, the backstops 84 will be raised on alternate forward strokes of the feeder bar 120 to achieve skip-feed operation.

Normally open contact R1 of relay R1, contact Fl of relay F, and the latch coil of relay N are connected in series between leads LL] and LL2 by lead 270; N.O. contact R1, contact F2, and the unlatch coil of relay N are also connected in series between leads LL] and LL2 by lead 272 connected to lead 270 between N.O. contact R1 and contact F1.

Normally closed contact R1 of relay R1, contact N1 of relay N, and the latch coil of relay F are connected in series by leads 274 and 276 between leads LL! and LL2; normally closed contact R1, contact N2, and the unlatch coil of relay F are also connected in series between LL] and LL2 by leads 274 and 278.

With switch 200 pulled to start and selector switch 202 in the skip-feed position, current will be supplied to DC. power supply 219, as previously explained, and current will be present in leads LLl and LL2. Assuming that vane switch 236 is open, current will not flow in lead 270 because N.O. contact R1 is open; current will flow along lead 274 because N.C. contact R1 is closed; current will not flow in lead 238 because contacts 244 are open. Thus, relay Rl remains de-energized.

Current in lead 274 will energize the unlatch coil of relay F through lead 278 and contact N2; this assures that relay F contacts F1 and F2 will assume the position shown in FIG. 5 at the beginning of the skip-feed sequence. This does not affect relay Nsince N.O. contact R1 is still open. Since contact F2G follows F2 and remains open, relay R2 will remain de-energized and its contacts will remain as shown in FIG. 5 with current flowing through N.C. contact R2 to coil C2 thereby maintaining backstops 84 in the raised position.

Since vane 238 continues to rotate, it enters slot 242 thereby closing contacts 244 of switch .236. This energizes relay R1 whose contacts R1 will reverse; thus, current will not flow in lead 274. This merely deenergizes the unlatch coil of relay F although its contacts F1 and F2'will remain latched in the position shown in FIG. 5. Contact F2G will remain open; relay R2 will remain de-energized so that current will continue to flow through N.C. contact R2 to coil Cl thereby maintaining backstops 84 in the raised position. However, current now flows through N.O. contact R1 and along lead 270 through contact F1 to the latch coil of relay N; energization of this coil reverses contacts N1 and N2 which will remain latched in a position opposite to that shown. Nothing more occurs since no current can flow in lead 274 with N.C. contact Rl being open.

At this time, vane 238 passes out of switch 236 thereby opening contacts 244 and de-energizing relay R1. Contacts Rl revert to their normal position as shown. No current can flow to relay N through N.O. contact R1 but will flow through N.C. contact R1 and leads 274 and 276 to the latch coil of relay F through contact N1, now closed; energization of this coil reverses contacts F1 and F2 to a position opposite to that shown. Contact F2G follows contact F2 so it closes thereby energizing relay R2 whose contacts R2 reverse to a position opposite to that shown. This supplies current to coil Cl through N.O. contact R2 thereby lowering backstops 84. I

On the next forward stroke of feeder bar 120, vane 238 again enters switch 236 thereby closing contacts 244 and energizing relay R1; its contacts R1 again reverse so that current is supplied to the unlatch coil of relay N through contact F2, now closed, and lead 272. Since contacts F1 and F2 remain latched, contact F2g remains closed, relay R2 remains energized and its N.O. contact R2 remain closed thereby supplying current to coil Cl so that backstops 84 remain in the lower position. However, energization of the unlatch coil of relay N reverses contacts N] and N2 to the position shown. Since N.C. contact R1 is now open because relay R1 is energized, relay F will not be energized even though contacts N1 and N2 have been reversed.

As vane 238 again passes out of switch 236, contacts 244 open, relay R1 is de-energized and contacts R1 revert to their normal state as shown. Current flows in leads 274 and 278 and through contact N2, now closed, to the unlatch coil of relay F. Energization of this coil reverses its contacts F1 and F2 to the position shown. Contact F2G follows contact F2 so it opens, deenergizing relay R2 whose contacts R2 revert to their normal position as shown thereby supplying current to coil Cl through N.C. contact R2 and raising backstops 84.

At this time, the cycle is completed and the condition of the circuit is the same as it was at the beginning of the sequence. Backstops 84 have been raised during alternate forward strokes of feeder bar thereby providing skip-feed operation. The foregoing sequence of operation continues so long as switch 200 in in the start position and selector switch 202 is the skipfeed" position.

OPERATION To operate the feeding machine 10, a blank is taken from the group of blanks to be fed and placed on the bed 12 with its leading edge 14 against the front guide faces 48. The front guides 46 are positioned across the support bars 44 and clamped at a distance somewhat narrower than the width of the blank. The front faces 48 of the front guides 46 are lowered to a position slightly greater than the thickness of the blank but less than the thickness of two such blanks and locked in place. The side guides 50 are positioned along the support bars 44 so that their side faces 54 rest loosely against the edges of the blank and are then locked in position.

The feeder bar assembly 26 is unclamped and positioned along the slides 122 so that the gripping edges 126 of the feed clips 124 or are slightly, for example one-fourth to one-half inch, behind the trailing edge 22 of the blank at the beginning of the feed stroke of the feeder bar; the feeder bar is then clamped in position.

The backstop assembly 20 is unclamped and locked in position along the T-slots 74 so as to support the trailing edge of the stack above the bed (see FIG. 4).

The valves 108 for the subchambers 92 lying outside the area of the blank are closed and all of the valves in the subchambers beneath the blanks are opened.

The vacuum pumps 98 are then turned on so that vacuum is applied to the subchambers 92 beneath the blank. The machine is jogged at a slow speed to feed the first blank. If feeding occurs properly, then the hopper defined by the front guides 46, side guides 50, the bed 12, and the backstop assembly 20 is filled with a stack of blanks 16 and the machine is then operated at a normal speed.

If the blank is thin or for some other reason is held too tightly against the perforated top 56, one of the vacuum pumps 98 may be turned off to reduce the static vacuum pressure beneath the blank. Holding the blank too tightly may cause damage to its trailing edge by the feed clips. lf the blank is still held too tightly against the perforated top, the dampers 97 may be slightly closed to further reduce the static pressure applied to the blank. These dampers may be further closed until satisfactory operation is achieved.

If the blanks are warped from front to back with the center portion of the blank resting against perforated top 56 and the leading and trailing edges curled upwards, it may be desirable to apply maximum air flow or dynamic negative pressure beneath the leading and trailing edges to urge them downward against the perforated top with less than maximum air flow applied to the center portion of the blank. This can be accomplished by rotating valves 108 to their fully open position in the subchambers 92 beneath the leading and trailing edges of the blank and partially closing the valves 108 beneath the center portion of the blank.

If the blanks are curled opposite to that just described, the valves can be positioned so that maximum air flow is applied beneath the center portion of the blank.

If the blanks are warped across the width of the support table 12, with their outside edges curled upward, the valves 108 may be positioned to apply maximum air flow beneath the outside edges and less than maximum beneath the center portion of the blank. If the edges of the blank are curled downward, maximum air flow can be applied beneath the center portion of the blank.

When large blanks are to be fed, access area support 111 is pivoted upward around forward pin assemblies 117 and rear pin assemblies 117 are engaged with grooves 119 to hold support 111 in a horizontal position flush with the top of bed 12. Pin assembly 123 on backstop assembly is engaged with support 111 so that the support is positioned automatically as the backstop assembly is positioned. The slide gate at the entrance to hose 115 is opened to supply vacuum to support 111. If a valve 108 is also included in support 111, it is also opened in the same manner as the remaining valves.

Thus, it is possible to control the dynamic air flow profile to draw the bottom blank downward against the perforated top 56 and backstops 84 in accordance with the particular warp characteristics of the. blanks by positioning valves 108. Once the blank is drawn against top 56, the holding force affecting advancement of the blank across the top by feeder 26 can be controlled by positioning dampers 97.

Although no particular number of subchambers 92 is required, it is obvious that a greater number provides a finer degree of control. For example, it has been found that corrugated paperboard can be fed satisfactorily by dividing support table 12 into subchambers 92 having a top surface area of about two-thirds to one square foot.

In the event of a jam-up or other malfunction of the feeder or adjacent processing machinery, the operator can quickly use the stop-feed pushbutton to raise the trailing edge of the stack. This prevents any further feeding of blanks, as previously explained, until the malfunction has been corrected and the push-button depressed to lower the trailing edge of the stack.

and

Should the blanks be longer than can be operated on by the adjacent machinery during one cycle of the machinery, the blank feeder may first be set up for operation as previously described. Thereafter, the operator can depress the skip-feed pushbutton to cause the trailing edge of the stack to be lifted on alternate strokes of the feeder bar assembly 26. Thus, one blank will be fed for each two forward strokes of the feeder assembly.

The foregoing has described improvements in blank feeding machines utilizing vacuum assistance which permits the feeding of extremely warped blanks with a minimum of attention and jam-ups. The invention has been shown in its best embodiment and mode of operation.

That which is desired to be claimed by Letters Patent 1. An improved method of feeding the bottom blank of a stack of blanks into adjacent processing machinery, comprising the steps of:

supporting a leading edge of said bottom blank at a first height for entry into said adjacent processing machinery;

supporting a trailing edge of said bottom blank at a second height above said first height;

applying subatmospheric pressure to substantially all of the underside of said bottom blank for urging said leading edge toward said first height and urging said trailing edge toward said second height;

engaging said trailing edge at said second height for advancing said bottom blank into said adjacent processing machinery; and,

simultaneously during advancement of said bottom blank,

providing an air flow beneath the underside of the next bottom blank of said stack beginning at the trailing edge thereof and continuing along said un' derside toward said leading edge.

2. The method of claim 1 including the additional step of regulating the magnitude of said subatmospheric pressure applied to the underside of said bottom blank.

3. The method of claim 1 including the additional step of regulating the magnitude of said air flow beneath the underside of said next bottom blank.

4. The method of claim 1 including the additional step of providing an air flow of a first magnitude beneath selected areas of said blank and an air flow of a second magnitude beneath the remaining areas of said blank.

5. The method of claim 1 including the additional step of lifting the trailing edge of said stack upon the occurrence of a malfunction in feeding said bottom blank.

6. The method of claim 1 including the additional step of cyclically lifting the trailing edge of said stack for feeding blanks at less than the normal rate.

7. An improved blank feeding machine for feeding the bottom blank of a stack of blanks into adjacent processing machinery, comprising in combination:

a first support means for supporting a leading edge of said bottom blank for entry into said adjacent processing machinery,

a second support means on said first support means for supporting a trailing edge of said bottom blank above said first support means;

vacuum means in said first support means for applying subatmospheric pressure to substantially all of the underside of said bottom blank for urging said leading edge against said first support means and urging said trailing edge against said second support means; and

advancing means on said first support means and beneath said stack for engaging said trailing edge to advance said bottom blank into said adjacent processing machinery,

said vacuum means providing an air fiow to the trailing edge of the next to be moved bottom blank of said stack for urging such edge against said second support means and continuing along said underside therefrom toward its leading edge beginning simultaneously with the advancement of said bottom blank.

8. The machine of claim 7 wherein said first support means comprises a feed table including a perforated top surface through which said subatmospheric pressure is applied to the underside of said bottom blank.

9. The machine of claim 8 wherein said feed table includes wear strips secured therein coacting with said advancing means to support said advancing means slightly above said perforated top surface.

10. The machine of claim 7 wherein said first support means includes an operator access area in the trailing edge thereof and an access area support for providing subatmospheric pressure to a portion of the underside of a stack of blanks above said access area support.

1 l. The machine of claim 7 wherein said second support means comprises a backstop bar on said first support means extending across the width of said first support means and including ledge support means for supporting the trailing edge of said stack above said first support means, said backstop bar being adjustable along said first support means toward said processing machinery for supporting the trailing edge of stacks of blanks of various preselected lengths.

12. The machine of claim 11 wherein said backstop bar includes stop-feed means for raising the trailing edge of said stack upon command to prevent engagement of said advancing means with said bottom blank.

13. The machine of claim 11 wherein said backstop bar includes cyclically operable lifting means for rais ing the trailing edge of said stack to prevent engagement of said advancing means therewith during alternate reciprocations of said advancing means.

14. The machine of claim 7 wherein said vacuum means comprises vacuum pump means connected to a vacuum chamber beneath said first support means for applying subatmospheric pressure through a plurality of perforations in said first support means to the underside of said bottom blank.

15. The machine of claim 14 wherein said vacuum chamber includes partitions forming a plurality of selectively operable subchambers beneath said perforations for applying subatmospheric pressure through selected areas of said first support means to the underside of said bottom blank.

16. The machine of claim 15 wherein selected ones of said subchambers are operable for preventing the application of subatmospheric pressure through portions of said perforated top surface lying outside the edges of said bottom blank.

17. The machine of claim 15 wherein selected ones of said subchambers include selectively operable valve means for supplying subatmospheric pressure to said subchambers.

18. The machine of claim 17 wherein selected ones of said valve means are adjustable for providing an air flow of a first magnitude through selected ones of said subchambers and of a second magnitude through others of said subchambers.

19. The machine of claim 7 wherein said vacuum means includes a pair of pump means both'connected to a vacuum chamber beneath said first support means, both of said pump means being selectively operable for applying more or less subatmospheric pressure through a plurality of perforations in said first support means to the underside of said bottom blank.

20. The machine of claim 19 wherein said vacuum means includes damper means for regulating the magnitude of said subatmospheric pressure applied to the underside of said bottom blank.

21. The machine of claim 20 wherein said damper means comprises a valve means in an air discharge opening of said pump means.

22. The machine of claim 19 wherein said vacuum means includes vent means between said pump means and said vacuum chamber for venting said vacuum means to atmosphere.

23. The machine of claim 7 wherein said advancing means comprises a feeder bar reciprocable along said top surface beneath said stack from the front of said second support means toward said processing machinery and includes a blank engaging means spaced above said first support means for engaging the trailing edge of said bottom blank and advancing the same into said processing machinery.

24. The machine of claim 23 wherein said blank engaging means includes a plurality of flexible feed clips spaced along the length of said feeder bar for resilient engagement with the trailing edge of said bottom blank.

25. The machine of claim 23 wherein said blank engaging means includes a plurality of rigid feed clips spaced along the length of said feeder bar for rigid engagement with the trailing edge of said bottom blank.

26. The machine of claim 23 wherein said feeder bar is reciprocable along said top surface for a distance of X inches from an initial position and the width of said bar along its'path of travel is one-half X or less.

27. Apparatus for performing the method of claim 1, comprising:

a first support means for supporting a leading edge of said bottom blank at a first height for entry into said adjacent processing machinery;

a second support means for supporting a trailing edge of said bottom blank at a second height above sadi first height;

vacuum means for applying subatmospheric pressure to substantially all of the underside of said bottom blank for urging said leading edge against said first support means and urging said trailing edge against said second support means; and

advancing means for engaging said trailing edge at said second height for advancing said bottom blank into said adjacent processing machinery,

. said vacuum means providing an air flow to the underside of the next bottom blank of said stack beginning at the trailing edge thereof and continuing toward said leading edge simultaneously during the advancement of said bottom blank.

28. An improved blank feeding machine for feeding the bottom blank of a stack of blanks into adjacent processing machinery comprising:

a bed having a front portion and a rear portion;

a backstop support above said rear portion of said bed for supporting a trailing end of said stack above said bed so that a leading end of said stack rests on said front portion of said bed and said trailing end rests on said support above said bed;

vacuum means for applying a suction to said bottom blank through said bed;

engaging means for selectively engaging the trailing edge of said bottom blank and advancing the same across said bed;

means for moving said engaging means toward and away from the front portion of said bed in strokes at a sine wave velocity so that the engagement of said engaging means and said bottom blank occurs at substantially zero velocity and maximum velocity is reached substantially at the midpoint of the forward movement of said engaging means,

said engaging means consituting a minor fraction of the top surface of said bed whereby the blank immediately above said bottom blank is progressively exposed to the suction applied through said bed from the trailing end of said blank immediately above to the leading end thereof.

29. The machine of claim 28 further including a front guide means above said front portion of said bed for defining a metered opening with said bed to limit the passage of blanks therebetween to only a single bottom blank of said stack.

30. The machine of claim 29 further including pull roll means behind said front guide means for engaging successive blanks passing through said metered opening at substantially their maximum velocity and advancing the same therethrough to further processing machinery. 

1. An improved method of feeding the bottom blank of a stack of blanks into adjacent processing machinery, comprising the steps of: supporting a leading edge of said bottom blank at a first height for entry into said adjacent processing machinery; supporting a trailing edge of said bottom blank at a second height above said first height; applying subatmospheric pressure to substantially all of the underside of said bottom blank for urging said leading edge toward said first height and urging said trailing edge toward said second height; engaging said trailing edge at said second height for advancing said bottom blank into said adjacent processing machinery; and, simultaneously during advancement of said bottom blank, providing an air flow beneath the underside of the next bottom blank of said stack beginning at the trailing edge thereof and continuing along said underside toward said leading edge.
 2. The method of claim 1 including the additional step of regulating the magnitude of said subatmospheric pressure applied to the underside of said bottom blank.
 3. The method of claim 1 including the additional step of regulating the magnitude of said air flow beneath the underside of said next bottom blank.
 4. The method of claim 1 including the additional step of providing an air flow of a first magnitude beneath selected areas of said blank and an air flow of a second magnitude beneath the remaining areas of said blank.
 5. The method of claim 1 including the additional step of lifting the trailing edge of said stack upon the occurrence of a malfunction in feeding said bottom blank.
 6. The method of claim 1 including the additional step of cyclically lifting the trailing edge of said stack for feeding blanks at less than the normal rate.
 7. An improved blank feeding machine for feeding the bottom blank of a stack of blanks into adjacent processing machinery, comprising in combination: a first support means for supporting a leading edge of said bottom blank for entry into said adjacent processing machinery, a second support means on said first support means for supporting a trailing edge of said bottom blank above said first support means; vacuum means in said first support means for applying subatmospheric pressure to substantially all of the underside of said bottom blank for urging said leading eDge against said first support means and urging said trailing edge against said second support means; and advancing means on said first support means and beneath said stack for engaging said trailing edge to advance said bottom blank into said adjacent processing machinery, said vacuum means providing an air flow to the trailing edge of the next to be moved bottom blank of said stack for urging such edge against said second support means and continuing along said underside therefrom toward its leading edge beginning simultaneously with the advancement of said bottom blank.
 8. The machine of claim 7 wherein said first support means comprises a feed table including a perforated top surface through which said subatmospheric pressure is applied to the underside of said bottom blank.
 9. The machine of claim 8 wherein said feed table includes wear strips secured therein coacting with said advancing means to support said advancing means slightly above said perforated top surface.
 10. The machine of claim 7 wherein said first support means includes an operator access area in the trailing edge thereof and an access area support for providing subatmospheric pressure to a portion of the underside of a stack of blanks above said access area support.
 11. The machine of claim 7 wherein said second support means comprises a backstop bar on said first support means extending across the width of said first support means and including ledge support means for supporting the trailing edge of said stack above said first support means, said backstop bar being adjustable along said first support means toward said processing machinery for supporting the trailing edge of stacks of blanks of various preselected lengths.
 12. The machine of claim 11 wherein said backstop bar includes stop-feed means for raising the trailing edge of said stack upon command to prevent engagement of said advancing means with said bottom blank.
 13. The machine of claim 11 wherein said backstop bar includes cyclically operable lifting means for raising the trailing edge of said stack to prevent engagement of said advancing means therewith during alternate reciprocations of said advancing means.
 14. The machine of claim 7 wherein said vacuum means comprises vacuum pump means connected to a vacuum chamber beneath said first support means for applying subatmospheric pressure through a plurality of perforations in said first support means to the underside of said bottom blank.
 15. The machine of claim 14 wherein said vacuum chamber includes partitions forming a plurality of selectively operable subchambers beneath said perforations for applying subatmospheric pressure through selected areas of said first support means to the underside of said bottom blank.
 16. The machine of claim 15 wherein selected ones of said subchambers are operable for preventing the application of subatmospheric pressure through portions of said perforated top surface lying outside the edges of said bottom blank.
 17. The machine of claim 15 wherein selected ones of said subchambers include selectively operable valve means for supplying subatmospheric pressure to said subchambers.
 18. The machine of claim 17 wherein selected ones of said valve means are adjustable for providing an air flow of a first magnitude through selected ones of said subchambers and of a second magnitude through others of said subchambers.
 19. The machine of claim 7 wherein said vacuum means includes a pair of pump means both connected to a vacuum chamber beneath said first support means, both of said pump means being selectively operable for applying more or less subatmospheric pressure through a plurality of perforations in said first support means to the underside of said bottom blank.
 20. The machine of claim 19 wherein said vacuum means includes damper means for regulating the magnitude of said subatmospheric pressure applied to the underside of said bottom blank.
 21. The machine of claim 20 wherein said damper means coMprises a valve means in an air discharge opening of said pump means.
 22. The machine of claim 19 wherein said vacuum means includes vent means between said pump means and said vacuum chamber for venting said vacuum means to atmosphere.
 23. The machine of claim 7 wherein said advancing means comprises a feeder bar reciprocable along said top surface beneath said stack from the front of said second support means toward said processing machinery and includes a blank engaging means spaced above said first support means for engaging the trailing edge of said bottom blank and advancing the same into said processing machinery.
 24. The machine of claim 23 wherein said blank engaging means includes a plurality of flexible feed clips spaced along the length of said feeder bar for resilient engagement with the trailing edge of said bottom blank.
 25. The machine of claim 23 wherein said blank engaging means includes a plurality of rigid feed clips spaced along the length of said feeder bar for rigid engagement with the trailing edge of said bottom blank.
 26. The machine of claim 23 wherein said feeder bar is reciprocable along said top surface for a distance of X inches from an initial position and the width of said bar along its path of travel is one-half X or less.
 27. Apparatus for performing the method of claim 1, comprising: a first support means for supporting a leading edge of said bottom blank at a first height for entry into said adjacent processing machinery; a second support means for supporting a trailing edge of said bottom blank at a second height above sadi first height; vacuum means for applying subatmospheric pressure to substantially all of the underside of said bottom blank for urging said leading edge against said first support means and urging said trailing edge against said second support means; and advancing means for engaging said trailing edge at said second height for advancing said bottom blank into said adjacent processing machinery, said vacuum means providing an air flow to the underside of the next bottom blank of said stack beginning at the trailing edge thereof and continuing toward said leading edge simultaneously during the advancement of said bottom blank.
 28. An improved blank feeding machine for feeding the bottom blank of a stack of blanks into adjacent processing machinery comprising: a bed having a front portion and a rear portion; a backstop support above said rear portion of said bed for supporting a trailing end of said stack above said bed so that a leading end of said stack rests on said front portion of said bed and said trailing end rests on said support above said bed; vacuum means for applying a suction to said bottom blank through said bed; engaging means for selectively engaging the trailing edge of said bottom blank and advancing the same across said bed; means for moving said engaging means toward and away from the front portion of said bed in strokes at a sine wave velocity so that the engagement of said engaging means and said bottom blank occurs at substantially zero velocity and maximum velocity is reached substantially at the midpoint of the forward movement of said engaging means, said engaging means consituting a minor fraction of the top surface of said bed whereby the blank immediately above said bottom blank is progressively exposed to the suction applied through said bed from the trailing end of said blank immediately above to the leading end thereof.
 29. The machine of claim 28 further including a front guide means above said front portion of said bed for defining a metered opening with said bed to limit the passage of blanks therebetween to only a single bottom blank of said stack.
 30. The machine of claim 29 further including pull roll means behind said front guide means for engaging successive blanks passing through said metered opening at substantially their maximum velocity and advancing the same therethrough to further procEssing machinery. 